Conveyer of endless belt type



Jan. 23, 1951 J. THOMSON CONVEYER 0F ENDLESS BELT TYPE Filed Oct. 22, 1947 1 y Mop. t b

R u E\\. I w hN J m *N .3 mm mm Q E\ .& Q m O\U m E R. Q 5% w 8 Ailomey increase or Patented Jan. 23, 1951 UNITED STATES PTENT OFFICE CONVEYER F ENDLESS BELT TYPE James Thomson, Glasgow, Scotland, as'signor to Mavor & Coulson, Limited, Glasgow, Scotland Application October 22, 1947, Serial No.- 781,392 In Great Britain October 12, 1945 Section 1, Public Law 690, August 8', 1946 Patent expires October 12, 1965 9 Claims.

This invention refers to conveyors of endless belt type, in which problems arise in maintaining the tension oi the so-called slac '1 stretch of the return run in relation to the full tension of the conveying run of the belt under load.

An object of this invention is to make provision whereby the full tension in a deflected portion of the endless belt going into the driving gear is caused to maintain a tensioning deflection in the form of a loop in the return run going out from the driving gear, the arrangement to be such that the first deflection varies with increase or decrease of the load imposed by the conveyor on the driving gear and therefore of the tension on the conveying run of the belt and such variation automatically causes a corresponding but amplified increase or decrease in the tensioning deflection.

Another object is to arrange that not only the deflected outgoing portion but also the deflected ingoing portion has the form of a loop, there bein accordingly one loop on each side of the driving gear and both connected by motionmultiplying' gear so that shortening of the ingoing loop under increased belt pull automatically causes lengthening of the outgoing loop to an amplified degree.

Another object is to have a belt-deflecting drum applied to the ingoing stretch of the return run, a belt-deflecting drum forming a lcop in the outgoing stretch, said drums to be each movable to decrease the degree of deflection formed by it in the belt, and means to connect said drums and yieldingly hold them against movement due to the tension of the deflected isa. plan corresponding to Fig. 2- but showing only the lower run of the conveyor.

Referring to the drawing, the endless conveyor belt is arranged in two runs, namely an upper run 4 and a lower run comprising a tensioned stretch 5 and a so-called slack stretch 6, between which two streirhes the driving gear op crates. In the example shown the upper run 4 is the conveying run and conveys from right to left (-inthe direction of the arrow' A,- Fig. I); and the lower run 5, 5 is the return run. The upper run 4 is as usual of trough form in crosssection, being supported by so-called troughing rollers 1 (shown only in Fig. 2). t opposite ends of the conveyor structure the belt passes around end rollers 8. The driving gear as usual comprises an electric motor 9, gearing (not shown) working in casings ill and H (Fig. 3) and a driving drum l2 wrapped by the lower run of the belt. A guide roller l3 leads the belt appropriately from the drum I2, the stretch 5 tra'v' elling into the driving gear and the stretch 6 travelling out from the gear. The driving gear is located at an intermediate portion in th lower run 5, E of thebelt.

Parts provided for the purpose of the invention include two loop-forming drums l4 and 15 each journalled in one of two bearing blocks l5 and H respectively slidable along guide bars i8 incorporated in the stationary structure of the conveyor. 'The drum ill forms the tensioned stretch 5 0f the return run into an approximately horizontal loop 2 l. Correspondingly the drum 5, with the aid of a guide drum 22 journalled in a stationary location on framework 23, forms the slack stretch 6 of the return run into an approximately horizontal loop 26.

The parts provided for the purposes of the invention also include a differential rope pulley assembly, comprising two small diameter pulleys 2'5 and two large diameter pulleys 26 all secured to a cross shaft 2'! j ournalled in a stationary location on framework 23. A pair of side ropes 29 are connected each at one end to the bearing block 16 and at the other end to the small diameter pulleys 25. correspondingly, another pair of side ropes 39 are connected each at one end to the bearing block ii and at the other end to the large diameter pulleys 26. The ropes 29 are wound on their pulleys 25 oppositely to the ropes 30 on their pulleys 2 6.

In use of the conveyor, the load on its conveying run 4 affects the tension of the belt, including the ingoing stretch 5 of the return run. That is to say, any increase in the load will tend to increase the tension in the stretch 5. However, if the tension in the stretch 5 increases, the loop 2i will become shortenedand will pull the drum- !4 and its block it towards the left; and the ropes 29 will force the pulley assembly 25, 26 to turn counter-clockwise (as viewed in Fig. 2). Thus, the ropes 20 from the pulleys 26 will pull the bearing block I! and its drum l5 so as to lengthen the loop 24 and take up slack in the outgoing stretch: 6 of the lower By virtue of'tlie "driving gear motion-multiplying action of the differential pulley assembly 25, 26, the loop 24 lengthens to an over-compensating extent, that is to say an extent greater than the loop 2! shortens, so that the drums M and i5 formin these loops tend to maintain a position of equilibrium; and a degree of tension appropriate to the load is maintained in the conveyor belt 4, 5, 8.

It Will be obvious that the motion-multiplying gear 25, 26 not only increases the length of the pull which said gear transmits from the ropes 29 to the ropes 30 but proportionately decreases the force of the pull which said gear transmits. Thus, the loop 24 formed in the lower run of the belt is subjected by the tensioning drum IE to a load that is substantially less than the load imposed by the loop 2| on the loop-forming drum l4.

Seeing that the conveyor must be capable of starting at a time when the conveying run 4 is either loaded or unloaded, it is desirable in regard to any horizontal conveyor according to the invention that provision should be made for applying light tension to the belt independently of the means controlling the loops 2| and 24. Such provision may take the form of any usual belt-tensioning device for adjusting, say, one of the terminal rollers 8.

I claim:

1. A conveyor comprising an endless belt, driving gear operating on the belt, a stretch of said belt subject to the tension of the conveying run going into the gear and another stretch of said belt subject to the lesser tension of the return run going out from the gear, a belt-deflecting drum applied to the ingoing stretch and movable in response to variations in the tension of the said drums are respectively journalled, said blocks being each movable under the influence of the tension applied to its drum by the looped stretch thereon in order to vary the length of the loop, and multiplying gear connecting said blocks so that a movement due to variation in load of the block whose drum is applied to the ingoing stretch produces a greater movement of opposite effect in the block whose drum is applied to the other stretch.

6. A conveyor as claimed by claim 5 in which the motion-multiplying gear consists of a small diameter pulley connected to the bearing block of the belt-looping drum applied to the ingoing stretch and a large diameter pulley connected to the other bearing block, said pulleys being interconnected to form a single rotatable assembly.

7. A conveyor comprising an endless belt, driving gear operating on said belt, a full-tensioned stretch thereof going into said gear and a lowertensioned stretch thereof going out from said gear, a first movable member applied to said ingoing stretch to loop a portion of it, a second movable member applied to said outgoing stretch to loop a portion of it, motion-multiplying means connecting said members and adapted to transmit to the second member from the first member, on movement thereof due to increase or decrease in the load imposed by the conveyor on the driving gear through said ingoing stretch, an overcompensating movement directed to increase or decrease the tension in the outgoing stretch and thus maintain the tension relationship between both of said stretches.

8. A conveyor comprising an endless belt with a conveying run and a return run, driving gear conveying run, a belt tensioning drum applied to gear ment of the drum applied to the outgoing stretch.

2. A conveyor as claimed by claim 1 in which the motion-multiplying gear is a diiferential pulley assembly comprising small diameter and large diameter pulleys having connections from said drums attached to said pulleys respectively in opposite directions.

3. A conveyor as claimed by claim 2 in which the small diameter and large diameter pulleys are respectively connected to the belt-deflecting drums applied to the ingoing and outgoing stretches of the belt.

4. A conveyor as claimed by claim 1 comprising also bearing blOckS in which the belt-defiecting drums are journalled, guide bars along which the bearing blocks are slidable to and from one another, and other drums co-operating with the belt-deflecting drums to form the belt into loops.

5. A conveyor comprising an endless belt formed into a conveying run and a return run, operating on the return run, a stretch of the return run going into the gear and another stretch of the return run going out from the gear, a, belt-looping drum applied'to the ingoing stretch, a belt-looping drum applied to the outgoing stretch, bearing blocks in which operating on said return run, a stretch thereof going into said gear and another stretch thereof going out from said gear, a first drum applied to said ingoing stretch to form a loop in a portion of it, a second drum applied to said outgoing stretch to form a loop in a portion of it, movable hearings in which said drums are respectively mounted, motion-multiplying gear, and means connecting said bearings to said gear, said connecting means and gear being adapted to transmit to the bearing of the second drum from the bearing of the first drum, on movement thereof due to increase or decrease in the load imposed by the conveyor on the driving gear through said ingoing stretch, an over-compensating movement directed to increase or decrease the tension in the outgoing stretch and thus maintain the tension relationship between both of said stretches.

9. A conveyor as claimed by claim 8 in which the motion-multiplying gear consists of an assembly of interconnected small and large pulleys rotatable as a unit, the small pulley being connected to the bearing of the first drum and the large pulley being connected to the other bearing.

JAMES THOMSON.

REFERENCES CITED The foilowing references are of record in the file of this patent:

UNITED STATES PATENTS Num er Name Date 417,512 Rosquist Dec. 17, 1889 1,540,720 Buckbee June 2, 1925 2,202,882 Wylie June 4,1940 

